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Marine Electronics


December 2013 Issue

Offshore Power Plant Runs On Low-Velocity Current
Minesto's (Belfast, Northern Ireland) step-change Deep Green 'underwater kite' marine power plant is now producing electricity in the waters off Northern Ireland. This is the first time a marine power plant designed for low-velocity currents is producing electricity at sea, anywhere in the world, according to the company.

'This is a break-through for the entire renewable energy industry,' said Minesto's CEO Anders Jansson. 'The challenge has been that the currents are too slow and the sites are too deep for most available marine power plants. Deep Green solves that problem.'

The ocean trials with a 1:4 scale Deep Green power plant in Strangford Lough proves power production from slow currents using a surface-mounted installation, a concept that is directly transferable to full commercial installations in ocean currents.

Minesto's goal is to produce renewable electricity with high reliability to a cost that will compete, or even be lower, than conventional energy sources.

The sea trial in Northern Ireland measures long-term performance of Deep Green for valuable insights for the first full-scale installation of Deep Green, planned for 2015 possibly somewhere in the U.K. The Deep Green demonstrator has a 3-meter-long wing and is tethered to an offshore control room in Strangford Lough.

Oyster 800 Producing Power From Wave Energy After Refit
Aquamarine Power (Edinburgh, Scotland) has announced initial electrical power production from its Oyster 800 wave energy convertor following the machine's return to service. During the summer, Oyster 800, located at the European Marine Energy Centre in Orkney, underwent a major refit, where new components including accumulators, valves, cables and subsea instrumentation connectors were replaced. The machine has been producing power in a series of controlled tests.

The company is continuing to test the safety systems of the plant and is slowly building up power production. In 60 hours of operations, 6 megawatt-hours of power have been produced. Output averaged about 100 kilowatts, with a peak output of 435 kilowatts. The longest continuous period of controlled power output was 22 hours.

NSF Grants $300,000 For Underwater Kite Research
A new research program directed by Dr. David Olinger, associate professor of mechanical engineering at Worcester Polytechnic Institute (WPI), has received a three-year, $300,000 grant from the National Science Foundation (NSF) to explore ways to harness ocean currents and tidal flows using underwater kites. The work is scheduled to begin in January.

'Unseen under the waves, winding along coastlines and streaming through underwater channels, there are countless ocean currents and tidal flows that bristle with kinetic energy,' Olinger said. 'And just as wind turbines can convert moving air into electricity, there is the potential to transform these virtually untapped liquid 'breezes' into vast amounts of power. For example, it has been estimated that the potential power from the Florida Current, which flows from the Gulf of Mexico into the Atlantic Ocean, is 20 gigawatts—equivalent to about 10 nuclear power plants.'

Olinger's new research builds on earlier work, funded by the NSF and the U.S. Environmental Protection Agency, in which he developed low-cost kite systems that use the wind to generate electricity or power simple devices like water pumps. Olinger's team developed computational models that can predict trajectories and power output for kites of different sizes and kite tethers of different lengths. The models can be used to design kites that can fly in stable, high-speed figure-eight patterns under changing wind conditions. Through the new NSF award, those algorithms will be applied to the design of kites that can 'fly' in underwater currents.

Using computational models, Olinger and his team will evaluate possible designs for undersea kites and explore methods for tethering them to floating platforms similar to those used for oil and gas rigs. They will also explore whether it is better for power generation, environmental impact and reliability to mount turbine generators directly to the kites or to place the generators on the platforms, connected to the kites by tethers that spin the generators as they spool and unspool on reels. In the final stage of the research, they will build scale models of the kites and test them in a water tank.

Reliant UUV Travels From Boston to New York
Bluefin Robotics Corp. (Quincy, Massachusetts), in support of the U.S. Naval Research Laboratory (NRL), has successfully completed a long-endurance UUV mission from Boston, Massachusetts, to New York, New York, totaling more than 100 hours with NRL's Reliant 'Heavyweight' UUV. The multiday mission exercised UUV autonomy methods and demonstrated the capability of a high-capacity energy configuration. The endurance test was designed to push the boundaries of traditional UUVs for new applications. The exercise is part of a series to support NRL's research in UUV-based technology for the U.S. Navy.

Reliant is an advanced version of the Bluefin-21 vehicle and, when equipped with a low-frequency broadband sonar payload, is the prototype SMCM UUV Knifefish system for the Navy. The vehicle navigates using a fiber-optic, gyro-based INS along with supplemental data from a GPS and Doppler velocity log. Reliant utilizes Bluefin's modular vehicle design that enabled the team to easily remove the payload section and add additional energy sections, increasing energy capacity to nearly 40 kilowatt-hours of power.

To optimize for endurance and range, the vehicle traveled at an average speed of 2.5 knots at 10 meters water depth, resurfacing every 20 kilometers for navigation updates over GPS. Vehicle status information was transmitted over Iridium satellite. While the support vessel was available, it did not provide navigational updates to the UUV, leaving the system to travel completely autonomously. After 109 hours of operation and transiting over 500 kilometers through strong currents, the system successfully reached New York Harbor with 10 percent of its battery life remaining.


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